Method and Device for Detecting Electric Arc Phenomenon on at Least One Electric Cable

ABSTRACT

The invention concerns a detecting device ( 1 ) comprising a database ( 10 ) including a plurality of membership classes, whereof one first class concerns a corona phase, and an assembly ( 5 ) comprising means for measuring electric current and electric voltage on an electric cable ( 2 ), means for filtering said measurements, and means for digitizing the filtered measurements and forming two digitized data segments, as well as an assembly ( 8 ) comprising means for subjecting each of the two segments to a number of functions to constitute a form vector, means for determining the membership class of said form vector, using the database ( 10 ), and means for deducing therefrom the presence or absence of an electric are phenomenon.

The present invention concerns a method and a device for detecting anelectrical arcing phenomenon on an electrical cable, for example a cableforming part of a bundle of electrical cables.

It is known that an electrical arcing phenomenon is the result of slowdeterioration of the insulation of cables used to distribute alternatingcurrent or direct current electrical energy caused by an aggressiveenvironment (moisture in the air, mildew, rubbing, vibration of theconnecting terminals, varying temperatures, shear, etc.).

The electrical arcing phenomenon is divided into four successive phasesof increasing energy:

-   -   a corona discharge phase corresponding to the birth of the        phenomenon;    -   a single-alternation conduction phase corresponding to a        dielectric breakdown with an increase of intensity;    -   a double-alternation conduction phase; and    -   an arc tracking phase. This last phase is a phase of electrical        discharge of limited intensity propagating along electrical        cables which may lead to the partial or total destruction of a        bundle of electrical cables as a result of carbonization of the        cable insulation.

Apart from deterioration of the insulation of an electrical cable, aloosened connection and abrasion of a cable are also propitious to theappearance of electrical arcs.

An object of the present invention is to detect an electrical arcingphenomenon in order to be able to avoid the harmful consequences thereofcited above.

There are known in the art protection devices called thermal cut-outsthat provide what is called “overcurrent” protection. However, the usualthermal cut-outs, which protect power supply cables if the energyconsumed by the connected load exceeds its nominal value, are unsuitablefor protection against arcing phenomena because of the low intensity atwhich the arc discharge phenomena occur and propagate over an electricalnetwork, that low intensity being insufficient to trigger said thermalcut-outs.

An object of the present invention is to remedy these drawbacks. Thepresent invention concerns a method of detecting an electrical arcingphenomenon on at least one electrical cable, for example a cable formingpart of a bundle of electrical cables, as soon as possible and in aparticularly efficacious manner.

To this end, according to the invention, said method is noteworthy inthat:

-   -   A/ in a preliminary step, there is determined a database        comprising a plurality of classes, including a first class        relating to a corona discharge phase to be detected and at least        one second class relating to phenomena liable to interfere with        the detection process; and    -   B/ in a subsequent detection step, successively:        -   a) in an acquisition phase:            -   α) an electrical current measurement and an electrical                voltage measurement are carried out directly on said                electrical cable;            -   β) said current and voltage measurements obtained in                this way are filtered; and            -   γ) the measurements filtered in this way are digitized                to form two digitized data segments relating to the                electrical current and to the electrical voltage,                respectively; and        -   b) in a subsequent processing phase:            -   α) each of said segments is subjected to a plurality of                particular functions each generating a scalar magnitude,                the set of scalar magnitudes relating to the current                forming a first vector and the set of scalar magnitudes                relating to the voltage forming a second vector;            -   β) using said database and a shape vector obtained from                said first and second vectors that is representative of                the measurements carried out, the class to which said                shape vector belongs is determined; and            -   γ) it is concluded that:                -   an electrical arcing phenomenon exists if said class                    represents said first class relating to a corona                    discharge phase; and                -   there is no electrical arcing phenomenon otherwise.

Accordingly, thanks to the invention, it is possible to detectefficaciously an electrical arcing phenomenon occurring on any type ofelectrical cable or bundle of electrical cables and in particular acable or a bundle of cables installed on an aircraft, for example anairliner.

Moreover, by detecting a corona discharge phase, it is possible todetect an electrical arcing phenomenon as soon as it arises (asindicated above, the corona discharge phase corresponds to the onset ofthe electrical arcing phenomenon), so that it is possible to take ingood time all the measures necessary to prevent arc tracking and theharmful consequences thereof cited above.

It will further be noted that the protection provided by the inventionmay be provided in conjunction with the usual “overcurrent” thermalprotection.

The corona discharge phase that the present invention takes into accountis characterized by:

-   -   low energy;    -   a band of high frequencies separate from and independent of the        mains frequency;    -   random amplitude, frequency and period; and    -   simultaneous effect on the voltage and the current.

The detection of a corona discharge phase is complex, in particularbecause of its random characteristics. Moreover, in an aeronauticalenvironment, i.e. when the cables under surveillance are installed on anaircraft, they are subjected to many kinds of high-intensity externalelectromagnetic attack (e.g. lightning) and low-intensityelectromagnetic attack (e.g. radar). As the corona discharge phenomenonis of low intensity, electromagnetic attack could degrade detectionquality and reliability and generate false triggering. Moreover, eachelectrical cable supplies a non-linear load generating distortions andcreating high-frequency harmonics (computer, landing lights, etc.) thatcould also potentially pollute the detection process. However, thanks tothe invention, it is possible to eliminate these risks by taking accountof classes to which the phenomena (in particular electromagneticphenomena and loads) that are liable to interfere with the detectionprocess belong, and by discriminating between the corona discharges tobe detected and these disturbing phenomena.

In one particular embodiment:

-   -   in the step B.a.α the current and voltage measurements are        carried out in a synchronized fashion, in order to preserve the        phase relationship between the current and the voltage; and/or    -   in the step B.a.β band-pass filtering is effected, in order to        eliminate the information relating to the power supply network;        and    -   the particular functions used in the step B.b.α have the object        of extracting interpretable main components of the signal (shape        vector) for comparison with said database; and/or    -   said shape vector is obtained by concatenation of said first and        second vectors.

In a preferred embodiment, in the step B.b.β there are determinedprobabilities of said shape vector belonging to respective classes ofsaid database and in the step B.b.γ it is concluded that an electricalarcing phenomenon exists if at least the following condition issatisfied: the probability of belonging to said first class is higherthan the probabilities thus determined.

In this case, the probabilities are determined advantageously with theaid of a Bayesian decision.

Moreover, in the step B.b.γ it is advantageously concluded that anelectrical arcing phenomenon exists if the following conditions are alsosatisfied:

-   -   the probability of belonging to said first class is above an        ambiguity threshold;    -   a probability density is greater than a predetermined value; and    -   a Mahalanobis distance is less than a predetermined value.

Moreover, in the step B.b.β it is advantageous if:

-   -   said shape vector is projected into a sub-space to obtain a        representative point having a reduced number of main components;        and    -   this point is projected into spaces representing the classes of        the database to obtain the corresponding probabilities of this        point belonging to said classes that is representative of the        shape vector.

Moreover, said database is advantageously formed by a training processin said preliminary step. Said database is advantageously formed frommeasurements carried out on electrical cables subject to phenomena forwhich it is required to constitute classes by implementation of at leastsaid steps B.a.α, B.a.β, B.a.γ and B.b.α.

The present invention also concerns a device for detecting an electricalarcing phenomenon on at least one electrical cable,

-   -   characterized in that it includes at least:        -   a database comprising a plurality of classes including a            first class relating to a corona discharge phase to be            detected and at least one second class relating to phenomena            liable to interfere with the detection process,        -   first means for carrying out an electrical current            measurement and an electrical voltage measurement directly            on said electrical cable;        -   second means for filtering said current and voltage            measurements;        -   third means for digitizing the filtered measurements to form            two digitized data segments relating to the electrical            current and to the electrical voltage, respectively;        -   fourth means for subjecting each of said segments to a            plurality of particular functions each generating a scalar            magnitude, the set of scalar magnitudes relating to the            current forming a first vector and the set of scalar            magnitudes relating to the voltage forming a second vector;        -   fifth means for determining the class to which a shape            vector obtained from said first and second vectors and            representative of the measurements carried out by said first            means belongs using said database; and        -   means for deducing the existence or non-existence of an            electrical arcing phenomenon from the result of the            processing carried out by said fifth means.

Furthermore, in one particular embodiment, said device further includes:

-   -   electrical power supply means connected to said electrical cable        that is being monitored and supplied with electrical power        thereby, avoiding having to provide a specific electrical power        supply for the detector device; and/or    -   a switching unit adapted to interrupt the current supplied by        said electrical cable that is being monitored automatically in        the event of detection of an electrical arcing phenomenon. Thus        the device according to the invention operates as a        circuit-breaker.

The device conforming to the invention has numerous advantages. Inparticular:

-   -   it detects in real time each arcing phenomenon that occurs on        any type of electrical cable as soon as that phenomenon arises;    -   it increases the reliability of the decision-making process and        therefore limits the probability of false alarms;    -   it increases the sensitivity of electrical arcing detection and        therefore protects the integrity of the electrical network; and    -   it immunizes the protection function from disturbing phenomena.

The figures of the appended drawings show how the invention may bereduced to practice. In these figures, identical reference numbersdesignate similar items.

FIG. 1 is a block schematic of a device of the invention.

FIGS. 2 and 3 are more detailed schematics of processing means of adevice of the invention.

The device 1 of the invention shown schematically in FIG. 1 is fordetecting an electrical arcing phenomenon on at least one electricalcable 2 forming part of a bundle of electrical cables, for example,before the electrical arc tracking that could lead to the partial ortotal destruction of a bundle of electrical cables, in order inparticular:

-   -   to increase safety;    -   to limit the consequences of an electrical discharge; and    -   if the cable under surveillance is installed on aircraft, in        particular an airliner, to protect the integrity of adjacent        cables without compromising the availability of the aircraft. In        this latter case, the device 1 is an onboard device.

Said electrical cable 2 that is being monitored is used to connect aload 3 of the usual kind to an electrical current generator 4 in theusual way.

According to the invention, said device 1 includes:

-   -   an acquisition unit 5 that is connected by connections 6 and 7        to said electrical cable 2;    -   an information processing unit 8 that is connected by a        connection 9 to said acquisition unit 5; and    -   a database 10 that is connected by a connection 11 to said        information processing unit 8. This database 10 comprises a        plurality of classes C1, C2, C3 of which a first class C1        relates to a corona discharge phase (see below) to be detected        and classes C2 and C3 relate to phenomena liable to interfere        with the detection process; in particular class C2 relates to        low-intensity electromagnetic attacks (radar fields, etc) and        class C3 relates to loads. Said database 10 is formed by a        training process during a preliminary step as described        hereinafter.

The corona discharge phase taken into account by the present inventionis characterized by:

-   -   low energy;    -   a band of high frequencies separate from and independent of the        mains frequency;    -   random amplitude, frequency and period; and    -   simultaneous effect on the voltage and the current.

As shown in FIG. 2, said acquisition unit 5 of the invention includes:

-   -   measuring means 12 and 13 of the usual kind connected to said        connections 6 and 7, respectively to measure directly the        electrical current in and the electrical voltage on said        electrical cable 2;    -   filter means 14 and 15 connected by respective connections 16        and 17 to said measuring means 12 and 13 and adapted to filter        said current and voltage measurements; and    -   means 18 and 19 connected by respective connections 20 and 21 to        said filter means 14 and 15 and adapted to digitize the        measurements filtered by said filter means 14 and 15 to form two        digitized data segments relating to the electrical current and        to the electrical voltage, respectively.

In one particular embodiment:

-   -   said measuring means 12 and 13 carry out synchronized current        and voltage measurements simultaneously in order to protect the        time relationship between the current and the voltage. The        voltage and the current are sampled with a shaping stage on the        phase that is being monitored; and    -   said filter means 14 and 15 apply band-pass filtering, for        example by means of a Fourier transform, in order to eliminate        information relating to the power supply network (current        generator 4); the filtering function extracts the spectral        components representative of the phenomena to be detected.

Moreover, as represented in FIG. 3, said information processing unit 8of the invention includes at least:

-   -   means 22 connected to the connection 9 which include a plurality        of particular integrated functions and are adapted to subject        each of said digitized data segments received from said means 18        and 19 to said plurality of particular functions. Each of said        particular functions supplies at the output a scalar magnitude.        The set of scalar magnitudes relating to the current then forms        a first vector and the set of scalar magnitudes relating to the        voltage forms a second vector. The object of said particular        functions is to extract the main components of the signal that        can be interpreted (shape vector) for comparison with the        database 10;    -   means 23 connected by a connection 24 to said means 22, for        determining the class to which a shape vector belongs, using        information coming from said database 10 and received via the        connection 11 and the shape vector obtained from said first and        second vectors and representative of the measurements effected        by said measuring means 12 and 13 on said electrical cable 2.        This shape vector is therefore representative of the electrical        state of said cable 2. More precisely, said shape vector is        obtained by concatenation of said first and second vectors        determined by the means 22; and    -   means 25 connected by a connection 26 to said means 23 for        deducing from the result of the processing carried out by said        means 23 the existence or non-existence of an electrical arcing        phenomenon at the level of said electrical cable 2.

More precisely:

-   -   said means 23 determine probabilities of said shape vector        belonging to the classes C1, C2 and C3 of said database 10; and    -   said means 25 conclude that an electrical arcing phenomenon        exists if at least the following condition is satisfied: the        probability of belonging to said class C1 (relating to the        corona discharge phase) is the highest of the probabilities        determined by said means 23.

As indicated above, the digitized data is recovered and processedsegment by segment. The device 1 therefore has two periodic measurementsegments (one for the current and one for the voltage). Said device 1determines if a corona discharge or corona discharge phase is presentfrom the mathematical combination of these two segments. Themathematical approach consists in effecting a classification of thecurrent and voltage measurements for the phase under scrutiny. Thegeneral idea is to extract the maximum information from the physicalphenomenon in order to be able to characterize it in amplitude,frequency and time. Several mathematical algorithms are used to dissectthe physical signal on the basis of the measurement segments. Eachalgorithm has its own transfer function. The means 23 use thecombination of all these results for shape recognition (see below).

Said means 23 function as classification means. To this end they usesaid shape vector characterizing the voltage and the current of thephase under scrutiny and said database 10 representing the phenomena tobe detected. The shape vector is projected into a subspace in order toreduce the number of main components of the shape vector. The point atthe reduced coordinates obtained in this way is then projected intoshape spaces representing said classes C1, C2 and C3 of the database 10.

It will be noted that a main component analysis (reducing the totalnumber of components) calculates the degree of redundancy betweenvariables describing the behavior of a phenomenon. An analysis of thiskind changes from a space with “m” dimensions to a space with “p”dimensions, where “m”>“p”. A study of the degree of redundancy betweenvariables enables the components (variables) to be sorted into sizeorder. After processing, the analysis supplies a matrix for passingbetween the space with “m” dimensions and the space with “p” dimensions.For example, at the beginning of the analysis there are six components(or variables) describing the three phenomena cited above (coronadischarges, electromagnetic interference, loads).

Said means 23 determine the probabilities of belong to a class citedabove with the aid of a Bayesian decision.

The Bayesian decision is based on a normal probability law, i.e. eachclass is modeled by a Gaussian distribution whose culminating point(epicenter) corresponds to the mean of the shape vectors. The measuringpoint that is projected into the plane of the database is subject to thefollowing calculations:

-   -   the distance between this measuring point and the epicenter of        the class C1;    -   the distance between this measuring point and the epicenter of        the class C2; and    -   the distance between this measuring point and the epicenter of        the class C3.

This kind of measurement is called a Mahalanobis distance measurement.When all the distances have been calculated, Bayes' theorem is used todetermine the a posteriori probability of belong to each of the classesC1, C2, C3. Only the maximum a posteriori probability is acted on.

This Bayesian decision is based on the following characteristics:A/ calculation of the a posteriori Bayes' probability:${P\left( {w_{i}/Z} \right)} = \frac{{p\left( {Z/w_{i}} \right)} \times {\Pr\left( w_{i} \right)}}{\sum\limits_{k = 1}^{n}\quad{{p\left( {Z/w_{k}} \right)} \times {\Pr\left( w_{k} \right)}}}$where:

-   -   w_(i): the class C1, C2, C3, i varying from 1 to n, n being        equal to 3 in the present example;    -   Pr(w_(i)): the a priori probability; and    -   p(Z/w_(i)): the probability density (for the normal law cited        above) specified hereinafter:        B/ measurement probability density:        ${p\left( {Z/w_{i}} \right)} = {\frac{1}{\sqrt{\left( {2\pi} \right)^{d} \times {\det\left( \sigma_{i} \right)}}} \times {\mathbb{e}}^{- {({\frac{1}{2}{({Z - \mu_{i}})}^{T}{\sigma_{i}^{- 1}{({Z - \mu_{i}})}}})}}}$        where:    -   T: indicates the transposed matrix;    -   d: the dimension of the input vector;    -   μ_(i): the moment of order 1 of the class i {i=1 to n];    -   σ_(i): the moment of order 2 of the class i;    -   w_(i): the class C1, C2, C3 concerned; and    -   Z: the measurement point resulting from an analysis into main        components in four dimensions;        C/ general Bayesian condition:        ${\sum\limits_{i = 1}^{n}\quad{P\left( {w_{i}/Z} \right)}} = 1$

Thus n a posteriori probabilities are obtained whose sum is equal to 1.

If a signal that does not belong to any of the classes C1, C2 and C3considered is injected at the input, the preceding equation will falsifythe calculation since by definition the sum is equal to 1 andconsequently the signal will be assigned a class anyway. Also, to avoidthis kind of problem, the means 23 employ a rejection strategy thatrefines the decision and therefore refines overall performance. Anobject of the rejection strategy is to fix boundaries at the decisionspace of the database 10 that is five-dimensional, for example. Thisamounts to creating a volume around the class C1. Bayes' theory gives aposteriori probabilities of which only the maximum probability is takeninto account. If that maximum probability corresponds to said class C1(corona discharge), said rejection strategy is applied, as the estimatemay be false.

To be more precise, thanks to this rejection strategy, for the means 23to assign a shape vector (representative of the measurements carried outon the cable 2) to the corona discharge class C1, it is necessary forall the following conditions to be satisfied:

-   -   the a posteriori probability supplied by Bayes' theorem is at a        maximum for the class C1, i.e. P(w₁/Z)>P(w₂/Z)>P(w₃/Z) or        P(w₁/Z)>P(w₃/Z)>P(w₂/Z), assuming that the class C1 has the        probability P(W₁/Z);    -   this latter probability is higher than an ambiguity threshold,        namely 0.33 in the case of three classes C1, C2 and C3;    -   the probability density of the normal distribution is greater        than 2×10⁻⁴; and    -   the Mahalanobis distance is less than 0.26.

Said means 23 also apply a thresholding procedure to the coronadischarge class C1. If the point considered belongs to the space (orvolume) corresponding to the criteria of belonging to the class C1, themeans 25 take an appropriate decision. That decision can take severalforms, as a function in particular of the degree of progress in time ofthe phenomenon.

Said means 25 can transmit this decision over a connection 27 toinformation means 28, for example a visual indicator (lamp), audioindicator or display screen adapted where applicable to inform anoperator of the detection of an arcing phenomenon.

Said means 25 can also command a switch 29 automatically over aconnection 30 to break automatically the current supplied by saidelectrical cable 2 that is being monitored to said load 3 in the eventof detection of an electrical arcing phenomenon at the level of saidelectrical cable 2.

Said device 1 further includes electrical power supply means 31connected by the connection 7 to said electrical cable 2 that is beingmonitored and supplied with electrical power thereby. The device 1 istherefore supplied with electrical power directly by the electricalcable 2 that is being monitored.

It will further be noted that said database 10 is formed by a trainingprocess from measurements carried out on electrical cables subject todifferent phenomena for which it is required to constitute classes usingat least the functions cited above of the acquisition unit 5 and themeans 22 and 23.

To constitute said database 10, recordings are effected in thelaboratory in order to obtain a set of measurements sufficientlyrepresentative of the different classes C1, C2 and C3 Considered. Therecords are subjected to the same mathematical processing as the futuremeasurements for which that database 10 will be used (see above).

The device 1 of the invention uses a classification and rejectionmechanism based on a statistic of the signal that can discriminate theelectrical arcing phenomenon from external interference. This device 1has numerous advantages. In particular:

-   -   it detects in real time each arcing phenomenon that occurs on        any type of electrical cable 2 as soon as that phenomenon        arises;    -   it avoids confusing corona discharges with the normal        consumption of a load;    -   it increases the reliability of the decision-making process and        therefore limits the probability of false alarms;    -   it increases the sensitivity of electrical arcing detection and        therefore protects the integrity of the electrical network; and    -   it immunizes the protection function from disturbing phenomena.

Moreover, said device 1 works for direct current and alternating currentelectrical networks, independently of the frequency of those electricalnetworks. Said device 1 is also independent of the type of loadconnected to the network that is being monitored.

1-14. (canceled)
 15. A method of detecting an electrical arcingphenomenon on at least one electrical cable (2), wherein: A/ in apreliminary step, there is determined a database (10) comprising aplurality of classes, including a first class relating to a coronadischarge phase to be detected and at least one second class relating tophenomena liable to interfere with the detection process; and B/ in asubsequent detection step, successively: a) in an acquisition phase: α)an electrical current measurement and an electrical voltage measurementare carried out directly on said electrical cable (2); β} said currentand voltage measurements obtained in this way are filtered; and γ) themeasurements filtered in this way are digitized to form two digitizeddata segments relating to the electrical current and to the electricalvoltage, respectively; and b) in a subsequent processing phase: α) eachof said segments is subjected to a plurality of particular functionseach generating a scalar magnitude, the set of scalar magnitudesrelating to the current forming a first vector and the set of scalarmagnitudes relating to the voltage forming a second vector; β) usingsaid database (10) and a shape vector obtained from said first andsecond vectors that is representative of the measurements carried out,the class to which said shape vector belongs is determined; and γ) it isconcluded that: an electrical arcing phenomenon exists if said classrepresents said first class relating to a corona discharge phase; andthere is no electrical arcing phenomenon otherwise.
 16. The method asclaimed in claim 15, wherein in the step B.a.α the current and voltagemeasurements are carried out in a synchronized fashion.
 17. The methodas claimed in either claim 15, wherein in the step B.a.β band-passfiltering is effected.
 18. The method as claimed in claim 15, whereinthe particular functions used in the step B.b.α have the object ofextracting interpretable main components of the signal for comparisonwith said database (10).
 19. The method as claimed in claim 15, whereinsaid shape vector is obtained by concatenation of said first and secondvectors.
 20. The method as claimed in claim 15, wherein in the stepB.b.β there are determined probabilities of said shape vector belongingto respective classes of said database (10) and in the step B.b.γ it isconcluded that an electrical arcing phenomenon exists if at least thefollowing condition is satisfied: the probability of belonging to saidfirst class is higher than the probabilities thus determined.
 21. Themethod as claimed in claim 20, wherein the probabilities are determinedwith the aid of a Bayesian decision.
 22. The method as claimed in claim20, wherein in the step B.b.γ it is concluded that an electrical arcingphenomenon exists if the following conditions are also satisfied: theprobability of belonging to said first class is above an ambiguitythreshold; a probability density is greater than a predetermined value;and a Mahalanobis distance is less than a predetermined value.
 23. Themethod as claimed in claim 20, wherein in the step B.b.β: said shapevector is projected into a sub-space to obtain a representative pointhaving a reduced number of main components; and this point is projectedinto spaces representing the classes of the database (10) to obtain thecorresponding probabilities of this point belonging to said classes thatis representative of the shape vector.
 24. The method as claimed inclaim 15, wherein said database (10) is formed by a training process insaid preliminary step.
 25. The method as claimed in claim 24, whereinsaid database (10) is formed from measurements carried out on electricalcables subject to phenomena for which it is required to constituteclasses by implementation of at least said steps B.a.α, B.a.β, B.a.γ andB.b.α.
 26. A device for detecting an electrical arcing phenomenon on atleast one electrical cable (2), wherein it includes at least: a database(10) comprising a plurality of classes including a first class relatingto a corona discharge phase to be detected and at least one second classrelating to phenomena liable to interfere with the detection process, afirst means (12, 13) for carrying out an electrical current measurementand an electrical voltage measurement directly on said electrical cable(2); second means (14, 15) for filtering said current and voltagemeasurements; third means (18, 19) for digitizing the filteredmeasurements to form two digitized data segments relating to theelectrical current and to the electrical voltage, respectively; fourthmeans (22) for subjecting each of said segments to a plurality ofparticular functions each generating a scalar magnitude, the set ofscalar magnitudes relating to the current forming a first vector and theset of scalar magnitudes relating to the voltage forming a secondvector; fifth means (23) for determining the class to which a shapevector obtained from said first and second vectors and representative ofthe measurements carried out by said first means (12, 13) belongs usingsaid database (10); and means (25) for deducing the existence ornon-existence of an electrical arcing phenomenon from the result of theprocessing carried out by said fifth means (23).
 27. The device asclaimed in claim 26, wherein it further includes electrical power supplymeans (31) connected to said electrical cable (2) that is beingmonitored and supplied with electrical power thereby.
 28. The device asclaimed in claim 26, wherein it further includes a switching unit (29)adapted to interrupt the current supplied by said electrical cable (2)that is being monitored automatically in the event of detection of anelectrical arcing phenomenon.